<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body {
            margin: 0;
            padding: 0;
        }
        div {
            width: 100%;
            height: 100%;
            background-color: red;
        }
    </style>
    <link rel="stylesheet" href="1.css">
</head>
<body>
    <div style="width: 300px;height: 300px; background-color: red;"></div>
</body>
</html>